A side view of a conventional hydraulic excavating machine, having a swivel base 22 on a crawler 21, is shown in FIG. 9. This swivel base 22 is equipped with an operator cab 23, an engine compartment 24 and a collapsible working machine 25. The operator cab 23 on such hydraulic excavating machine is installed off-center with respect to the center O of the swivel base 22, as shown in FIGS. 10 and 11. A hinge type door 26 of the operator cab 23, for an operator to access the inside of the operator cab 23, is opened by pivoting the door 26 to a fully-opened position as shown with a 2-dotted broken line in FIG. 10. A slide type door 26 is opened by sliding it to a fully-opened position as shown with the 2-dotted broken line in FIG. 11.
However, if the opening for the hinge type door is large-sized, it presents the problem that the door protrudes beyond the turning radius R of the upper swivel body when the door is kept open and fixed, and can therefore be damaged due to collision or bumping with other external objects during a swiveling operation.
In the case of the slide type door, the rails and rollers employed to slide the door occupy space within the operator cab, and therefore the internal space of the operator cab is reduced. As the construction machine is generally operated with its door kept open in summer, there is a problem in that it is difficult to fix the door without any play when it is kept open, since there is inevitably some play in the mechanism of such slide type door.